Many packet communication protocols, such as Ethernet, and Internet Protocol (IP), allow for errors in data packets, and dropped packets. A receiver which discovers missing packets or data errors requests the transmitter to re-transmit the problem data packets. Typically, the problem data packets are eventually received later than they should have.
E1 signals usually transmit real time data, such as voice, and are considered high priority signals. Introducing errors, or dropping any data from these signals, should be avoided.
The term “communication channel” in all its forms is used throughout the present specification and claims interchangeably with the terms “channel” and “signal” and their corresponding forms.
Many point-to-point communication systems carrying high priority signals communicate at a data rate appropriate for a worst case reception scenario, in order not to drop the high priority signals. This is a waste of capacity most of the time, and increases the cost of such systems.
Adaptive Coding and Modulation (ACM) enables changing data rate of a communication system in response to time varying conditions such as interference and fading.
ACM is widely used in packet communication protocol systems such as wireless LAN (WiFi) and wireless MAN (WiMAX). Such systems reduce their data rate in response to interference and fading. During the process of reducing the data rate, data packets are typically lost and have to be retransmitted.
US Published Patent Application 2006/0077994 of Spindola et al describes systems and methods for adapting a de jitter buffer to conform to air link conditions. An air link characteristic may be detected before that characteristic begins to affect packet delivery, such as by slowing or speeding delivery delay at a subscriber station. A receiver-side de-jitter buffer, which adds delay to received packets, may adaptively adjust its size based upon the detected air link characteristic, such that the de jitter buffer is appropriately sized for anticipated data packets before they are received at the subscriber station.
US Published Patent Application 2006/0109856 of Deshpande describes an adaptive buffering scheme that supposedly allows more effective media transport and buffering. In one aspect of the adaptive buffering scheme, buffering parameters are adapted to different media characteristics, such as media play commands or the amount of encoding/transcoding required for the particular media stream. In another aspect of the adaptive buffering scheme, buffering is adapted to different transmission or memory conditions, such as transmission rate, packet jitter, or the amount of available buffer memory. In one example, the adaptive buffering is supported using Real Time Streaming Protocol (RTSP), and/or Real Time Transport Protocol (RTP) and associated Real Time Control Protocol (RTCP), and/or Session Description Protocol (SDP) messages.
The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.